The present invention is directed to a cutting member for use in material removal tools, such as drills, cutting disks, saws and the like where the cutting member is formed of binder agents, hard material particles and diamond grains.
Material removal tools are used for drilling, cutting and severing of rock and building materials, such as concrete, brick and the like and such tools have cutting edges formed of separate cutting members connected to a carrier in the shape of a hollow cylinder, a disk, a roller and the like. The cutting members consist of binder agents, hard material particles and diamond grains.
A rock drill is disclosed in DE-PS 590 707 which has an annular or core bit formed of sintered hard metal. The hard metal consists of hard metal particles sintered together with the use of a small amount of a binder agent. Diamond grains are embedded in the surface of the annular bit for the purpose of removing material.
The useful life of the rock drill with a core bit or annular bit of the above-mentioned type is determined by the service life of the diamond grains. If the diamond grains are abraded by wear, the bit is no longer able to carry out its material removing function. Further, it should be considered that the core bit formed of sintered hard material provides an extremely hard carrier for the diamond grains, however, it has only a slight toughness or ductility. As a result, all of the blows occurring during the drilling operation are transmitted by the diamond grains, without any damping, to the hard carrier, whereby excessive stresses develop very rapidly, so that the diamond grains fracture prior to their normal wear period with the result that the bit fails prior to the end of its normal useful life.
A hollow drill is disclosed in DE-OS 34 08 092, and has a hollow cylindrical carrier or support with an open end at the drilling end containing cutting members. The cutting members of this known hollow drill consists of a binder with diamond grains embedded in it.
In this hollow drill, the diamond grains are not only present at its surface but also within the entire cutting member comprising the binder. If this drill is used for removing material, the binder is also worn away in addition to the wear of the diamond grains. If a diamond grain has been completely worn away or if it fails, then at the same time some of the binder has been removed, whereby an additional diamond grain is exposed for carrying out the material removing function. The useful life of this known hollow drill ends only after the cutting member is completely worn down. In addition, the binder provides such an elastic carrier or support for the diamond grains that blows developed in the drilling operation can be absorbed without causing overstress and, as a result, does not lead to premature fracture of the diamond grains.
The annular drill bit disclosed in the above-mentioned patent publication has certain advantages as far as useful life is concerned as compared to the bit mentioned at the beginning. These advantages operate within a specific frame of reference and, in particular, are greatly influenced by the material being worked. If such material is a very hard concrete, the wear of the diamond grains and especially of the binder is so great that disadvantages have to be accepted relating to the reduced useful life.